This invention relates to a method for preparing compositions of matter that are useful as catalysts, and to a method of using these catalysts for polymerizing addition polymerizable monomers. More particularly the present invention relates to an improved method for preparing a class of catalysts known as constrained geometry catalysts.
In U.S. Ser. No. 545,403, filed Jul. 3, 1990, (published in equivalent form 3/13/91 as EP-A-416,815) there are disclosed certain constrained geometry metal complexes and catalysts derived by reacting the metal complex with activating cocatalysts. In U.S. Pat. 5,064,802 (published 3/20/91 in equivalent form as EP-A-418,044) there are disclosed certain further constrained geometry metal catalysts formed by reacting such metal complexes with salts of Bronsted acids containing a noncoordinating compatible anion. The reference discloses the fact that such complexes are usefully employed as catalysts in addition polymerizations. In U.S. Ser. No. 720,041, filed Jun. 24, 1991, now abandoned an alternative technique for preparing cationic constrained geometry catalysts by anion abstraction using borane compounds is disclosed. For the teachings contained therein, the foregoing United States patent and applications are herein incorporated by reference.
It has been previously known in the art to employ carbonium, oxonium or sulfonium ions to generate cationic bis-cyclopentadienyl Group 4 metal catalysts. Such a process is disclosed in EP-A2 426,637 published May 8, 1991.
It would be desirable if there were provided an improved method that would allow the production of even more efficient catalysts as well as an improved addition polymerization process utilizing such catalysts.